Specifications

Section 2—Modbus Plus Overview Bulletin No. VVDED397044US R12/00

MSTR Block December 2000

Top Node Content

The 4x register entered in the top node is the first of nine contiguous

holding registers that comprise the control block (see Table 11).

NOTE: You must understand MODBUS PLUS routing path procedures

before programming an MSTR instruction. For a complete overview, refer

to the

MODBUS PLUS Network Planning and Installation Guide,

890 USE 100 00

Middle Node Content

The 4x register entered in the middle node is the first in a group of

contiguous holding registers that comprise the data area.

• For operations that provide the communication processor with data—

such as a write operation—the data area is the source of the data.

• For operations that acquire data from the communication processor—

such as a read operation—the data area is the destination for the data.

Bottom Node Content

The integer value entered in the bottom node specifies the length—the

maximum number of registers—in the data area. Although the typical

MODBUS PLUS length may range from 1 to 100 registers, the ATV58

drive controller range is 1 to 60 registers.

Table 11: Control Block Holding Registers

Displayed Identifies one of the nine MSTR operations

1st implied Displays error status

2nd implied Displays length

3rd implied Displays MSTR operation-dependent information

4th implied

Routing 1 register, used to designate the address of the destination

node for a network message transaction.

5th implied Routing 2 register

6th implied Routing 3 register

7th implied Routing 4 register

8th implied Routing 5 register